Document the return values of Size
Document the return values of Size

With this change it much clearer which return values are the width and the height.
gdamore/termbox-go,wkjagt/termbox-go,pwiecz/termbox-go,wallyqs/termbox-go,wallyqs/termbox-go,nsf/termbox-go,wkjagt/termbox-go,michaeldv/termbox-go,nsf/termbox-go,gdamore/termbox-go,michaeldv/termbox-go,pwiecz/termbox-go